Characteristics of an inductively coupled plasma source using a parallel resonance antenna

Abstract

We report experimental results from a new inductively coupled plasma (ICP) source for next generation plasma processing. The new source, which we have called a parallel resonance antenna, is designed to reduce problems caused by a large antenna inductance and to improve the plasma density uniformity for large area processing. The key techniques of this new source are reduction of the inductance of the antenna system in parallel connection and induction of LC-resonance with external capacitance variation. The parallel connection of the coils reduces the antenna inductance and the low inductance decreases the antenna voltage. In addition, it allows the antenna size to be easily scaled up to a 300 mm process. An external variable capacitor is connected in series to an outer coil to obtain good plasma uniformity. Because the current distribution in each coil is adjusted by varying the external capacitance, the radial profile of the plasma density can be controlled. The LC-resonance effect is elucidated by observing the reduction in the antenna voltage and variation in the current in the outer coil. We can control the radial plasma density with 3% uniformity by only varying the external capacitance with various discharge powers and pressures. The plasma parameters measured by the rf-compensated Langmuir probe show properties similar to those of general ICPs. These results are consistent with previous modelling work.